Seat-operated controls for tractors are already known in the art. They are used to shut off the power going to the implement on the tractor when the operator has left his seat. The seat is usually spring-loaded to move upwardly when the operator gets off the seat, and that upward movement controls elements responsive to the upward movement and which in turn control the power to implements or the like. For instance, U.S. Pat. No. 3,590,564 shows this type of seat controlled or safety device for lawn mowers mounted on a tractor, whereby the absence of the operator on the operator's seat actuates linkage to shut off the flow of power to the mower. However, these are two springs pulling in opposite directions to secure an idler pulley in an operative or inoperative position, and a handle overrides the springs. Further, that patented arrangement relies upon the relative strength of the two springs operating on an over-center lever arrangement, and the springs also are controlled by the vertical movement of the operator's seat, so those springs must serve a dual purpose. In those respects, the present invention differs from that shown in that patent, and the present invention provides for a spring-loaded operator's seat which directly and positively controls a manual control connected with a hydraulic valve which in turn governs the power to the tractor-mounted implement. As such, the present invention is of a nature different from that of the prior art and it is a control for accurate positioning of a hydraulic valve stem.
Other examples of the prior art utilizing control of power through the operator's seat are seen in U.S. Pat. Nos. 2,612,232 and 3,229,452 and 3,736,729 and 3,969,875 and 4,178,741. Those patent disclosures differ from the present invention in that they do not disclose the direct control of hydraulic power by means of the operator's seat and they basically relate to electric controls. U.S. Pat. No. 4,178,741 only shows an elaborate system of electric switches and solenoids for operating a hydraulic system under certain conditions, and it does not disclose a seat-operated safety device which position the system to the inoperative mode when the seat is unoccupied, all as in the present invention.
Generally speaking, the present invention relates to an improved and simplified seat-operated hydraulic valve control which positions the hydraulic valve in an inoperative position when the seat is unoccupied. By this arrangement, the hydraulic system which controls the implements on the tractor becomes inoperative when the operator gets off the seat. However, the control can be arranged such that while it precludes implement operation it can still allow for hydraulic power for other purposes, such as raising and lowering the implements, or the like, even though the operator is not occupying the seat. Thus, if the operator intentionally gets off the seat or falls off the seat the control operates to interrupt the hydraulic power to the implement, and it also allows the operator to operate the implement when he is not occupying the seat.
Further, the control arrangement of this invention also provides for a type of interlock switch which must be in a set position before the power can be commenced, and that set position can be established by the positioning of the control in the neutral position relative to powering the implement. In that regard, there is an additional safety feature in this invention.